Multi-scale analysis of recruitment of a coral reef fish on the Great Barrier Reef

The potent~al causes of the variable nature of recrultment of marlne organisms can be Inferred from the scales over which they vary Sampllng for recrults of Chaetodon ralnfordi on the Great Barrier Reef, Austral~a, was done at the end of the recruitment season In 3 yr at 3 spatial scales: at reglons separated by hundreds of km, at reefs separated by up to tens of km; and at different sites on 1 coral reef. Desplte a background of var~ability suggesting the influence of stochastlc processes, the data showed considerable pattern, implicating the involvement of determlnlstlc processes. At each spatial scale, recruitment was higher In 1985 than 1986 or 1987 Furthermore, d e s p ~t e the general reduction In recrultment wlth tlme, the dlstr~bution patterns lvere consistent In each year. Southern regions always had hlgher rates of recrultment than northern onvs, some reefs always received higher rates than neighbouring ones and some sites consistently had higher rates than others only hundreds of met]-es away. Recruitment rates of C. ralnfordi were attributed to settlement rates Consequently, the observed patterns were related, at each spatial scale, to either the ava~lability of pre-settlement fish, or habitat selection actlng at the time of settlement. Thls study tvas not able to dlstlnguish between such alternative hypotheses at any scale, but lncilcated the types of studies requlred to do so